1. Field of the Invention
The present invention relates to a valve operating apparatus for an internal combustion engine and, more specifically, to apparatus to cause the engine valve to operate or not to operate depending on the energization state of a solenoid actuator.
2. Description of the Prior Art
Variable valve control systems for multiple valve engines wherein the intake and/or exhaust valves can either be selectively actuated or actuated at selected lift profiles, are well known in the art. Example systems are shown in U.S. Pat. Nos. 4,151,817 and 4,203,397 the disclosures of which are hereby incorporated by reference except those portions which also incorporate by reference. U.S. Pat. No. 4,151,817 discloses a primary rocker arm element engageable with a first cam profile, a secondary rocker arm element engageable with a second cam profile, and means to interconnect or latch the primary and secondary arm elements. U.S. Pat. No. 4,203,397 discloses an apparatus to selectively engage or disengage an engine poppet valve so as to connect or disconnect the valve from the rest of the valve gear using a latch mechanism thereby causing the valve to operate or remain stationary.
A particular problem exists in prior art systems which operate a valve train which incorporates hydraulic lash adjusters in that means must be provided to prevent the lash adjuster from overly expanding or "pumping up" when the valve is in its inactive mode and there is essentially no resisting force applied by the valve spring. In prior art systems it has been necessary to provide an auxiliary contact surface on the rocker arm structure which is maintained in engagement with a base circle cam portion formed on the camshaft to prevent the lash adjuster from overly expanding.
Prior art methods and mechanisms tend to be slow in response, bulky, expensive and have high actuation force and are unreliable. Selective valve actuation systems are designed to selectively engage intake and/or exhaust valves to better match the power output of an engine for a motor vehicle to the load for improved efficiency and fuel economy.